JFreechart has been the leading library for drawing variety of charts in Java for years. This chart generation framework can be used to draw almost kinds of charts with high quality, flexibility and great level of customizations. In this tutorial, we show you how to use JFreechart to draw line chart - one of the most commonly used chart types. In addition, some basic customizations are provided for your convenience. We will have the following chart finally:NOTE: To use JFreechart in your project, add the following JAR files to the project’s classpath:
jcommon-VERSION.jar
jfreechart-VERSION.jar
1. A Java Swing program for line chart example
The following Java class creates a simple Swing program that displays a JFrame window which contains a chart panel:
/**
* This program demonstrates how to draw line chart with CategoryDataset
* using JFreechart library.
* @author www.codejava.net
*
*/
public class LineChartWithCategoryDatasetExample extends JFrame {
public LineChartWithCategoryDatasetExample() {
super("Line Chart Example with JFreechart");
JPanel chartPanel = createChartPanel();
add(chartPanel, BorderLayout.CENTER);
setSize(640, 480);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
}
private JPanel createChartPanel() {
// creates a line chart object
// returns the chart panel
}
private CategoryDataset createDataset() {
// creates chart dataset...
// returns the dataset
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new LineChartWithCategoryDatasetExample().setVisible(true);
}
});
}
}
This is just a skeleton, as you can see the createChartPanel() and createDataset() methods don’t have any implementations.
2. Creating a dataset
Write code for the createDataset() method as follows:
This creates some dummy data for a DefaultCategoryDataset which is required by the ChartFactory.createLineChart() method. The data is added to the dataset in the following form:
Each series has values are associates with categories. As shown in the above code, we create four series (namely Java, PHP, C++ and C#). The categories are times (2005, 2006 …) and the values are popularity degrees (5.0, 4.6, 3.2 …).In reality, the data can be loaded from database, text files, CSV files, Excel files, etc.
3. Creating a line chart
Write code for the createChartPanel() method as follows:
The following screenshot is taken when running the above Swing program that creates the line chart using the first method:The second variant of the createLineChart() method allows us to specify the plot orientation, show/hide the legend box… Here’s an example:
Often times, the chart’s default look and feel doesn’t suite one’s needs. So here are some customization examples provided for your references.Basically, we get a reference of the plot from the chart to do the customizations on the plot instance:
CategoryPlot plot = chart.getCategoryPlot();
Setting custom renderer for the series lines:
LineAndShapeRenderer renderer = new LineAndShapeRenderer();
plot.setRenderer(renderer);
Output:
Setting custom paint color and stroke for each series line:
LineAndShapeRenderer renderer = new LineAndShapeRenderer();
// sets paint color for each series
renderer.setSeriesPaint(0, Color.RED);
renderer.setSeriesPaint(1, Color.GREEN);
renderer.setSeriesPaint(2, Color.BLUE);
renderer.setSeriesPaint(3, Color.YELLOW);
// sets thickness for series (using strokes)
renderer.setSeriesStroke(0, new BasicStroke(4.0f));
renderer.setSeriesStroke(1, new BasicStroke(3.0f));
renderer.setSeriesStroke(2, new BasicStroke(2.0f));
renderer.setSeriesStroke(3, new BasicStroke(1.5f));
plot.setRenderer(renderer);
Output:
Setting custom paint color and stroke for the plot’s outlines (chart borders):
And here is the result of all the customizations above:
5. Saving the chart as an image
The ChartUtilities class provides some methods which we can use to export the chart graphics to an image file. For example, the following code snippet saves the chart to a PNG image file:
File imageFile = new File("LineChart.png");
int width = 640;
int height = 480;
try {
ChartUtilities.saveChartAsPNG(imageFile, chart, width, height);
} catch (IOException ex) {
System.err.println(ex);
}
To save as JPEG image, use the saveChartAsJPEG() method.
Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He began programming with Java back in the days of Java 1.4 and has been passionate about it ever since. You can connect with him on Facebook and watch his Java videos on YouTube.
NOTE: To use JFreechart in your project, add the following JAR files to the project’s classpath:
The second variant of the createLineChart() method allows us to specify the plot orientation, show/hide the legend box… Here’s an example:
The createLineChart3D() methods allow us to draw a 3D line chart. For example:
Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He began programming with Java back in the days of Java 1.4 and has been passionate about it ever since. You can connect with him on Facebook and watch his Java videos on YouTube.
LineChartWithCategoryDatasetExample.java
Comments
I'm sorry my English is so bad.
Yes, such tutorial will be coming soon. Thanks for asking.